Catheter with body locking into cannula hub

ABSTRACT

A system for introducing a fine bore catheter into a vein includes a cannula unit comprising an elongate tubular sheath, defining a distal end and a proximal end, and a hub enclosing the proximal end of the sheath. The cannula unit is adapted to receive an introducing needle for introducing the distal end of the sheath of the cannula into a vein. The system also includes a catheter unit, having a distal end and a proximal end, a body portion located at the proximal end of the catheter unit, and a catheter tube extending from the body portion to the distal end of the catheter unit. The hub of the cannula unit defines guide means adapted to receive and guide the distal end of the catheter tube into the proximal end of the cannula sheath so that the catheter tube can be guided into and then fed along the sheath, and the hub of the cannula is adapted to receive and enclose at least a portion of the body of the catheter in a locking arrangement which substantially prevents the catheter body moving relative to the hub of the cannula unit.

This application is a 371 of PCT/AU96/00236 filed Apr. 23,1996.

FIELD OF THE INVENTION

This invention relates to fine bore catheter and to a system forinserting a fine bore catheter into a vein.

BACKGROUND OF THE INVENTION

As used in this specification and in the appended claims, the term finebore catheter tube means a catheter tube having an outside diameter ofless than 2.0 mm and an internal bore of less than 1.5 mm. Similarlyfine bore catheter means a catheter having a fine bore catheter tube.

Fine-bore silicone catheters allow long term phlebitis (inflammation)free infusion of intravenous nutrition into peripheral veins such as legand arm veins. They also create less trauma to a patent's body tissuethan a larger bore catheter and have a wider range of applications thana larger bore catheter. Such a fine-bore catheter can be as effective asa larger bore catheter centrally placed in a main vein in the torso orchest of a patient such as infraclavicular sub clavian or jugular vein.Placing a larger catheter in a main vein has inherent risks: inparticular sepsis and thrombosis can occur. Dedicated specialisedsupport teams are required to monitor patients subjected to centralvenous cannulation yet the risks persist. However, because of theproblems associated with introducing fine bore catheters into peripheralveins, central venous cannulation, despite the potentially lifethreatening risks, remains the current method of choice foradministration of intravenous nutrition.

The current method of placing catheters in peripheral veins requirestaxing hand to eye coordination and uses risky "catheter through needle"techniques with which it is possible to cut the catheter tube on theneedle being used to introduce the catheter in a peripheral vein andthus requires specially trained personnel. Hence central venouscannulation despite the potential life threatening risks remains thecurrent method of choice for administration of intravenous nutrition.

The present invention seeks to provide an improved system for theinsertion of very fine catheters into veins, particularly peripheralveins

SUMMARY OF THE INVENTION

According to the present invention there is provided a system forintroducing a fine bore catheter into a vein including:

a cannula unit comprising an elongate tubular sheath, the sheathdefining a distal end and a proximal end, the cannula unit furthercomprising a hub enclosing the proximal end of the sheath, the cannulaunit being adapted to receive an introducing needle for introducing thedistal end of the sheath of the cannula into a vein; and

a catheter unit, the catheter unit having a distal end and a proximalend, a body portion located at the proximal end of the catheter unit,and a catheter tube extending from the body portion to the distal end ofthe catheter unit characterised in that the catheter tube is a fine borecatheter tube, in that the hub of the cannula unit defines guide meansadapted to receive and guide the distal end of the catheter tube intothe proximal end of the cannula sheath so that the catheter tube can beguided into and then fed along the sheath, and in that the hub of thecannula is adapted to receive and enclose at least a portion of the bodyof the catheter in a locking arrangement which substantially preventsthe catheter body moving relative to the hub of the cannula unit.

Conveniently the proximal end of the catheter defines a luer lock orsimilar means for attaching the proximal end of the catheter to asyringe or other fluid delivery device.

It is preferred that the bore of the lumen of the catheter is ofconstant diameter from the proximal end to the distal end. This reducesthe risk of blood products clotting the bore of the lumen.

It is preferred that the external diameter of the catheter is between0.6 mm and 1.2 mm.

The internal bore of the catheter may be 0.3 to 0.8 mm.

It is preferred that the system includes a introducing needle forinsertion into the cannula for piercing a vein. The needle comprises aneedle having a distal end adapted to pierce a vein and the proximal endof the needle is mounted in a hollow hub.

The invention also provides a catheter unit, having a distal end and aproximal end, including a body portion located at the proximal end ofthe catheter unit, and a catheter tube extending from the body portionto the distal end of the catheter unit characterised in that thecatheter tube is a fine bore catheter tube, and in that at least aportion of the body of the catheter is adapted to be received andenclosed in the hub of a cannula in a locking arrangement whichsubstantially prevents the catheter body moving relative to the hub ofthe cannula unit.

The invention also provides a cannula unit for use in conjunction withthe catheter as described above comprising an elongate tubular sheath,the sheath defining a distal end and a proximal end, the cannula unitfurther comprising a hub enclosing the proximal end of the sheath, thecannula unit being adapted to receive an introducing needle forintroducing the distal end of the sheath of the cannula into a vein; andcharacterised in that the hub of the cannula unit defines guide meansadapted to receive and guide the distal end of a catheter tube into theproximal end of the cannula sheath so that the catheter tube can beguided into and then fed along the sheath, and in that the hub of thecannula is adapted to receive and enclose at least a portion of the bodyof the catheter in a locking arrangement which substantially preventsthe catheter body moving relative to the hub of the cannula unit.

Although the present invention is particularly suited to use with finebore catheters the structure of the system can also be used with largebore diameter catheters. Thus the present invention also provides asystem for introducing a catheter into a vein including:

cannula unit comprising an elongate tubular sheath the sheath defining adistal end and a proximal end, the cannula unit further comprising a hubenclosing the proximal end of the sheath, the cannula unit being adaptedto receive an introducing needle for introducing the distal end of thesheath of the cannula into a vein; and

a catheter unit, the catheter unit having a distal end and a proximalend, a body portion located at the proximal end of the catheter unit,and a catheter tube extending from the body portion to the distal end ofthe catheter unit characterised in that the hub of the cannula unitdefines guide means adapted to receive and guide the distal end of thecatheter tube into the proximal end of the cannula sheath so that thecatheter tube can be guided into and then fed along the sheath, and inthat the hub of the cannula is adapted to receive and enclose at least aportion of the body of the catheter in a locking arrangement whichsubstantially prevents the CF body moving relative to the hub of thecannula unit.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example only and withreference to the accompanying drawings in which:

FIG. 1 is a schematic drawing of an introducing needle unit:

FIG. 2 is a schematic drawing of a cannula unit;

FIG. 3 is a schematic drawing of a catheter unit;

FIG. 4 is a guide wire:

FIG. 5 is a perspective drawing of an introducer needle unit, a cannula,and catheter partially inserted into that cannula:

FIG. 6 is a plan view of the needle unit shown in FIG. 5;

FIG. 7 is a sectional view on line VII of FIG. 6;

FIG. 8 is a plan view of the cannula shown in FIG. 5;

FIG. 9 is a side elevation of the cannula shown in FIGS. 5 and 8;

FIG. 10 is a sectional view on line X--X shown in FIG. 9;

FIG. 11 is a sectional view on line XI--XI shown in FIG. 8;

FIG. 12 is a plan view of the catheter shown in FIG. 5;

FIG. 13 is a sectional view on line XIII--XIII of FIG. 12:

FIG. 14 is a side elevation of the catheter shown in FIG. 12:

FIG. 15 is a front view of the catheter shown in FIG. 12: and

FIG. 16 is a sectional view on lines XVI--XVI shown in FIG. 15.

SPECIFIC DESCRIPTION OF THE BEST METHOD FOR PERFORMING THE INVENTION

Referring to the drawings, the principle of operation of the presentinvention will be described with reference to FIGS. 1 to 4.

FIG. 1 shows an introducing needle unit, or trocar, 10. The needle unitincludes a stainless steel needle 11 having a distal end 12 defining abevel portion which is adapted to pierce a vein or the like. The other,or proximal end, 13 of the needle is embedded in a hub 14. The hub 14 isrotationally symmetrical about the longitudinal axis defined by theneedle 11 and includes a clear flash back chamber 16. The proximal end17 of the needle unit is open but is adapted to receive a breathingfilter or stopper, if required. The distal end 18 of the hub is semiellipsoid in shape.

FIG. 2 shows an introducing cannula unit 20. The cannula unit includesan elongate sheath, or tube 21 having an annular cross section anddefining a cylindrical bore 22. The cannula unit has a proximal end 20Aand a distal end 20B. The tube 21 is embedded in a hub 24. The hub isgenerally rotationally symmetrical about a longitudinal axis defined bythe elongate tube 21. From the proximal end 20A the hub defines a mainbody portion 26 which is cylindrical, a conical portion 28 which taperstowards to a further cylindrical portion 30 which is substantiallynarrower than the main body portion 26 and has a slightly largerdiameter than the outside diameter of the elongate tube.

Two diametrically opposed planar wings 31A, 31B extend outwards from themain body portion 26 in a plane parallel to and passing through thelongitudinal axis defined by the tube 21.

As is shown in phantom (i.e. in broken lines) at the proximal end 20A ofthe cannula unit, the hub defines a cavity 32 which is in the shape of atruncated ellipsoid. The proximal or open end 33 of the cavity is of areduced diameter compared with the maximum diameter of the ellipsoid.The narrower end of the cavity 34, being the end distal from theproximal end of the cannula tapers gradually to define a bore which isthe same diameter as the bore 22 of the tube. The tube 21 extends intothe hub as far as that end 34 of the cavity.

The hub is made of a plastics material and thus is deformable Theellipsoid cavity is dimensioned so that the distal end 18 of the hub ofthe needle unit will securely locate in the cavity, with somedeformation of the hub.

The length of the tube 21 is such that if the needle unit is insertedthrough the tube 21 with the distal portion 18 of the hub located in thecavity 32, the distal end or bevel portion 12 of the needle will justprotrude from the distal end 20B of the tube 21.

FIG. 3 shows a fine bore catheter 50 and FIG. 4 shows a guide wire 80for use with that catheter 50.

The catheter has a proximal end 50A and a distal end 50B.

At the proximal end 50A of the catheter, there is a luer lock 51 toenable the proximal end 50A of the catheter to be connected to asyringe, or the like. From the luer lock to the distal end of thecatheter, the catheter body comprises a first cylindrical portion 52which is stepped out to the base of a truncated conical section 54,which tapers to a further cylindrical portion 56 followed by a generallyellipsoid protrusion or plug 58. A fine bore silicone catheter tube 53having an external diameter of 1.1 mm and an internal bore of diameter0.8 mm extends from the junction of the conical portion 54 and thecylindrical portion 56 of the catheter body through the ellipsoidportion 58 and extends beyond that ellipsoid portion. The total lengthof the fine bore catheter tube is approximately 150 mm.

In use, the introducing needle unit 10 shown in FIG. 1 is fitted intothe introducing cannula unit 20 with the ellipsoid portion 18 fittinginto the cavity 32 to securely locate the needle unit in the cannulaunit. The distal end 12 of the needle 11 protrudes just beyond thedistal end 20B of the elongate tube 21 of the introducing cannula unit.The needle can then be used to insert the tube 21 of the cannula unitinto a peripheral vein of a patient. The clear hub 16 allows the personinserting the cannula into the vein to see when blood flashes back intothe hub 16 which indicates that the cannula is located in the vein. Theneedle unit is then removed from the cannula unit. The catheter, withthe guide wire 80 inserted through the bore of the catheter to stiffenthe catheter tube can then be inserted into the cannula. Theconfiguration of the cavity 32 and in particular the configuration ofthe distal end 34 of the cavity assists in guiding the catheter tubethrough the sheath of the cannula unit and reduces the amount of taxinghand to eve coordination necessary for introducing the catheter into avein. When the catheter is fully inserted into the vein the ellipsoidportion 58 snap fits into the cavity 32 and maintains the catheter unitfirmly attached to the cannula unit.

The fact that the docking device 58 securely fits into the cavityenables the cannula and the catheter to be taped together to a patientsskin using the wings 31A and 31B of the cannula, as single unit. Thiseliminates the possibility of shearing of the catheter unit relative tothe cannula unit which could occur if the cannula and catheter wereseparately taped to the skin.

Also, when correctly inserted into a vein, no portion of the fine boresilicone tube is exposed. This eliminates the possibility of the tubekinking.

Once the catheter is properly inserted and fixed to a patient's skin theguide wire is removed and the luer lock 51 can be connected to asuitable intravenous feeding mechanism.

FIGS. 5 to 16 show perspective and other views of a second embodiment ofthe present invention which operates on the same principle as theembodiment described in relation to FIGS. 1 to 4, although the design ofthe components is different.

FIGS. 5 to 7 show a second embodiment of an introducing needle unit 100.The needle unit has a proximal end 100A and a distal end 100B. From theproximal end 100A of the needle unit the hub defines a main body portion102 which is generally cylindrical but which is contoured with a seriesof circumferentially extending ribs 103, a conical portion 104 and anenlarged bulbous portion 106 which is generally ellipsoid. The proximalend of the cylindrical body portion defines a central bore 108 which isa standard luer taper. The bore can accept a breathing filter orstopper. As can be seen from FIG. 6 the needle extends from the distalend of the needle unit into the body of the hub as far as the junctionbetween the conical portion and the cylindrical portion.

The needle is approximately 51 mm long and is made of surgical stainlesssteel. The hub of the needle unit is made from polycarbonate and isformed around the needle in a mould to manufacture the introducingneedle unit 100.

FIGS. 9 to 12 show introducing a cannula unit 120 in more detail. Thecannula has a proximal end 120A and a distal end 120B. It comprises aelongate sheath or tube 121 defining a cylindrical bore 122, and a hubportion generally indicated at 124. From the proximal end 120A the hubdefines a generally bell shaped portion 126 followed by a generallycylindrical portion 128 from which extend two flat wing portions 130 and132. As can be seen in FIGS. 10 and 11, the bell shaped portion 126defines a generally bell shaped internal cavity 136 having an endportion 138 adjacent the tube 122 and a depending skirt portion 140. Ascan best be seen in FIG. 11 two slots 141A. 141B extend from theproximal end 120A of the hub of the cannula unit through the skirtportion 140. The slots are diametrically opposed on either side of thecentral axis of the cannula as defined by the bore 122 of the tube 121.The distal end of each slot terminates in an enlarged generally circularopening 142A, 142B, respectively.

The body of the cannula is made from moulded flexible nylon and thesheath of the cannula is made from polyamide tubing which isultrasonically welded to the body of the cannula.

FIGS. 12 to 16 show the catheter unit 150 in more detail. The catheterunit has a proximal end 150A and a distal end 150B. Starting at theproximal end 150A of the catheter the body portion of the catheterdefines a luer lock 152, a cylindrical portion 154, an annular rib 156,a generally cylindrical portion 158 but which includes opposed contouredsurfaces 159A, 159B for grip, a second annular rib 160 of a slightlylarge diameter than the first annular rib, and a conical portion 162which tapers towards a generally ellipsoid shaped protrusion or plug164. As best seen in FIGS. 12 and 15 at the end of the catheter bodyportion remote from the proximal end of the catheter 150A, twodiametrically opposed cylindrical stubs 166A, 166B protrude from thecatheter.

The body of the catheter is polycarbonate. The catheter tube is glued tothe catheter body by clear RV2 medical grade adhesive which is insertedinto slot 170 shown in FIGS. 12 and 13.

The procedure for use of this second embodiment of the present inventionis the same as that for the catheter shown in FIGS. 1 to 4. Theintroducing needle unit 120 is inserted in the introducing cannula unit150 and the cannula unit and needle unit inserted into a vein. Theneedle is then removed from the cannula unit and the catheter fed intothe cannula with the internal shape of the bell shaped cavity in thecannula unit acting as a guide means for assisting in guiding thesilicone catheter tube 151 into the bore of the cannula. A guide wire 80is used to stiffen the catheter tube. The stubs 166a, 166B on eitherside of the catheter hub pass along the slots 126A, 126B in the cannulaenlarging the slots by pushing the two portions of the bell shapedportion apart and snap fit into the circular holes 142A, 142B. Thisprevents both rotation of the catheter hub in the cannula andlongitudinal movement of the catheter relative to the cannula, inaddition to the locking provided by the engagement of the ellipsoidportion 164 of the catheter in the correspondingly configured cavity 136in the cannula. The catheter is thus locked to the cannula and thecannula can be taped to the skin of a patient.

The present invention provides a cannula unit which is specially shapedto guide a fine bore catheter into a vein without the need for taxinghand to eve coordination which is normally required when inserting finebore catheters into veins.

The locking of the catheter and the cannula unit together, prevents thecatheter from moving relative to the cannula and thus prevents shearing.

The catheter bore is of a constant diameter from the luer lock to thedistal end of the catheter and this reduces the risk of blood productsclotting the catheter bore.

The locking device on the catheter not only allows rapid attachment ofthe catheter to the cannula to produce a firmly locked device that canbe fixed to the skin of the limb or truck of a person with tape but alsoprovides protection from kinking or shearing of the catheter tube,since, inter ilia, none of the catheter tubing is exposed.

The following table shows exemplary dimensions for parts of the systemshown in FIGS. 5 to 16.

    ______________________________________    Introducing Needle                Catheter Tube  Cannula Sheath    Outside           Internal Outside  Internal Bore                                     Internal                                            Outside    Diameter           Bore     Diameter Diameter                                     Diameter                                            Diameter    ______________________________________    0.600 mm           0.400 mm French   0.350 mm                                     0.700 mm                                            0.850 mm                    Gauge 2                    0.64 mm    0.800 mm           0.600 mm French   0.600 mm                                     1.000 mm                                            1.150 mm                    Gauge 3                    0.90 mm     1.00 mm           0.800 mm French   0.900 mm                                     1.300 mm                                            1.450 mm                    Gauge 4                    1.19 mm    ______________________________________

All the components of the system described above should be resistant togamma sterilisation.

Although the above embodiments are described in terms of a fine borecatheter, it will be appreciated that although the invention isparticularly suited to use with fine bore catheters the invention isalso applicable to catheters having larger bores and diameters than finebore catheters.

It will be appreciated by persons skilled in the art that numerousvariations and/or modifications may be made to the invention as shown inthe specific embodiments without departing from the spirit or scope ofthe invention as broadly described. The present embodiments are,therefore, to be considered in all respects as illustrative and notrestrictive.

The claims defining the invention are as follows:
 1. Apparatus forintroducing a fine bore catheter into a vein including a cannula unitcomprising an elongate tubular sheath, the sheath defining a distal endand a proximal end, the cannula unit further comprising a hub enclosingthe proximal end of the sheath, the cannula unit being adapted toreceive an introducing needle for introducing the distal end of thesheath of the cannula into a vein; anda catheter unit, the catheter unithaving a distal end and a proximal end, a body portion located at theproximal end of the catheter unit, and a catheter tube extending fromthe body portion to the distal end of the catheter unit characterised inthat the catheter tube is a fine bore catheter tube having an outsidebore less than 2.0 mm, in that the hub of the cannula unit defines guidemeans adapted to receive and guide the distal end of the catheter tubeinto the proximal end of the cannula sheath so that the catheter tubecan be guided into and then fed along the sheath, and in that the hub ofthe cannula is adapted to receive and enclose at least a portion of thebody of the catheter in a locking arrangement which substantiallyprevents the catheter body moving relative to the hub of the cannulaunit.
 2. Apparatus as claimed in claim 1 characterised in that the hubof the cannula defines a generally ellipsoid cavity or socket and theportion of the body of the catheter unit which is closest to the distalend of the catheter unit defines a generally ellipsoid protrusion orplug which is adapted to snap fit into the ellipsoid cavity to securethe catheter to the cannula.
 3. Apparatus as claimed in claim 1characterised in that the system includes an introducing needle unitadapted to locate inside the cannula sheath for use in inserting thecannula into a vein.
 4. Apparatus as claimed in claim 2 characterised inthat the hub of the cannula is generally bell shaped and defines a skirtportion and in that at least one slot extends through the skirt portionfrom the proximal end of the hub towards the distal end of the cannulaparallel to the longitudinal axis of the hub and in that a stub extendsfrom the ellipsoid portion of the catheter body which is adapted tolocate in the slot the portion of the main body of the catheter which isinserted into the hub thereby assisting in guiding the main body of thecatheter into the hub of the cannula and preventing rotation of thecatheter body relative to the cannula hub.
 5. Apparatus as claimed inclaim 4 characterised in that a pair of diametrically opposed slots areprovided in the skirt of the cannula and a pair of corresponding stubsextend from the catheter and in that the width of the stubs is greaterthan the width of the slot body so that the slots are enlarged as thestubs pass along the slots and in that the distal end of each slot isenlarged so that each stub snap fits into the enlarged distal ends ofeach respective slot.
 6. Apparatus as claimed in claim 1 characterisedin that the diameter of the bore of the catheter unit is substantiallyconstant from the distal end of the catheter to a luer lock at theproximal end of the main body of the catheter.
 7. Apparatus as claimedin claim 1 characterised in that the catheter tube is silicone and hasan outside diameter of between 0.6 mm and 1.2 mm and an internal borediameter of 0.3 mm to 0.8 mm.
 8. Apparatus as claimed in claim 1characterised in that the body of the catheter defines a slot whichreceives adhesive to secure the catheter tube to the body of thecatheter.
 9. A catheter unit, having a distal end and a proximal end,including a body portion located at the proximal end of the catheterunit, and a catheter tube extending from the body portion to the distalend of the catheter unit characterised in that the catheter tube is afine bore catheter tube having an outside diameter of less than 2.0 mmand in that at least a portion of the body of the catheter is adapted tobe received and enclosed in the hub of a cannula in a lockingarrangement which substantially prevents the catheter body movingrelative to the hub of the cannula unit.
 10. A cannula unit for use inconjunction with the catheter of claim 9 comprising an elongate tubularsheath, the sheath defining a distal end and a proximal end, the cannulaunit further comprising a hub enclosing the proximal end of the sheath,the cannula unit being adapted to receive an introducing needle forintroducing the distal end of the sheath of the cannula into a vein; andcharacterised in that the hub of the cannula unit defines guide meansadapted to receive and guide the distal end of a catheter tube into theproximal end of the cannula sheath so that the catheter tube can beguided into and then fed along the sheath, and in that the hub of thecannula is adapted to receive and enclose at least a portion of a bodyportion of the catheter in a locking arrangement which substantiallyprevents the catheter body moving relative to the hub of the cannulaunit.
 11. Apparatus for introducing a catheter into a vein including:acannula unit comprising an elongate tubular sheath, the sheath defininga distal end and a proximal end, the cannula unit further comprising ahub enclosing the proximal end of the sheath, the cannula unit beingadapted to receive an introducing needle for introducing the distal endof the sheath of the cannula into a vein; and a catheter unit, thecatheter unit having a distal end and a proximal end, a body portionlocated at the proximal end of the catheter unit, and a catheter tubeextending from the body portion to the distal end of the catheter unitcharacterised in that the hub of the cannula unit defines guide meansadapted to receive and guide the distal end of the catheter tube intothe proximal end of the cannula sheath so that the catheter tube can beguided into and then fed along the sheath, and in that the hub of thecannula is adapted to receive and enclose at least a portion of the bodyof the catheter in a locking arrangement which substantially preventsthe catheter body moving relative to the hub of the cannula unit. 12.Apparatus as claimed in claim 11 characterised in that the hub of thecannula defines a generally ellipsoid cavity or socket and the portionof the body of the catheter unit which is closest to the distal end ofthe catheter unit defines a generally ellipsoid protrusion or plug whichis adapted to snap fit into the ellipsoid cavity to secure the catheterto the cannula.
 13. Apparatus as claimed in claim 12 characterised inthat the system includes an introducing needle unit adapted to locateinside the cannula sheath for use in inserting the cannula into a vein.14. Apparatus as claimed in claim 13 characterised in that the hub ofthe cannula is generally bell shaped and defines a skirt portion and inthat at least one slot extends through the skirt portion from theproximal end of the hub towards the distal end of the cannula parallelto the longitudinal axis of the hub and in that a stub extends from theellipsoid portion of the catheter body which is adapted to locate in theslot the portion of the main body of the catheter which is inserted intothe hub thereby assisting in guiding the main body of the catheter intothe hub of the cannula and preventing rotation of the catheter bodyrelative to the cannula hub.
 15. Apparatus as claimed in claim 14characterised in that a pair of diametrically opposed slots are providedin the skirt of the cannula and a pair of corresponding stubs extendfrom the catheter and in that the width of the stubs is greater than thewidth of the slot body so that the slots are enlarged as the stubs passalong the slots and in that the distal end of each slot is enlarged sothat each stub snap fits into the enlarged distal ends of eachrespective slot.
 16. Apparatus as claimed in claim 15 characterised inthat the diameter of the bore of the catheter unit is substantiallyconstant from the distal end of the catheter to a luer lock at theproximal end of the main body of the catheter.
 17. Apparatus as claimedin claim 16 characterised in that the catheter tube is silicone and hasan outside diameter of between 0.6 mm and 1.2 mm and an internal borediameter of 0.3 mm to 0.8 mm.
 18. Apparatus as claimed in claim 17characterised in that the body of the catheter defines a slot whichreceives adhesive to secure the catheter tube to the body of thecatheter.